The Plague

Why it matters for the novel

The Great Plague of 1665 is a turning point in Daniel’s story and in Newton’s. Cambridge closes, sending Newton home to Woolsthorpe where he has his annus mirabilis — inventing calculus, discovering the composition of light, and formulating gravity, all in about eighteen months. Daniel, left behind, witnesses London’s devastation firsthand. The plague is also the event that makes the Waterhouse family’s Puritan fatalism feel reasonable: when a third of your city dies in a summer, apocalyptic theology isn’t abstract.

The Great Plague of London (1665)

The last major outbreak of bubonic plague in England. It killed an estimated 75,000-100,000 Londoners — roughly a quarter of the city’s population — between spring 1665 and winter 1666. At its peak in September 1665, over 7,000 people died in a single week.

How it spread

Plague is caused by the bacterium Yersinia pestis, carried by fleas on black rats. Nobody in the 17th century knew this. Theories ranged from bad air (“miasma”) to divine punishment to astrological influence. Quarantine was practiced — houses with plague victims were sealed shut with the inhabitants inside, a red cross painted on the door — but it was crude and often just ensured entire families died together.

The response

The court and anyone who could afford to fled London. Charles II moved to Oxford. The Royal Society suspended meetings. Trade collapsed. The poor, who couldn’t leave, died in enormous numbers. Daniel Defoe’s A Journal of the Plague Year (1722), though written decades later, drew on firsthand accounts and remains the most vivid description.

Newton’s annus mirabilis

When Cambridge closed in 1665, the 22-year-old Isaac Newton went home to Woolsthorpe Manor in Lincolnshire. Over the next eighteen months, working entirely alone, he:

• Developed the “method of fluxions” (calculus)
• Conducted prism experiments proving white light is composed of colors
• Began formulating the law of universal gravitation (the famous apple story dates to this period, though the apple probably didn’t hit him)

It may be the most productive eighteen months in the history of science. Newton told no one about most of it for years.

The broader context

The 1665 plague was the last major European outbreak, but plague had been a recurring terror since the Black Death of 1347-1351, which killed roughly a third of Europe’s population. London had major outbreaks in 1563, 1593, 1603, and 1625. Each time, the pattern was the same: summer heat, rat populations, explosive spread, mass death, winter retreat. The 1665 outbreak ended partly because the Great Fire of London (1666) destroyed much of the old city — and with it, the rat habitats.

For the characters in Quicksilver, plague isn’t a historical curiosity. It’s a lived memory that shapes how they think about God, nature, cities, and mortality.